This invention relates to a process for crystallizing potassium chloride. In particular, this invention relates to a process for enhancing the crystal size and distribution of potassium chloride crystals.
It is known to recover potassium chloride from brines containing the potassium salt as well as other salts. It is also well recognized in the art that crystal habit modification is frequently desirable or necessary to obtain crystals having a desired size distribution and shape. Particularly, it is frequently desirable to produce crystals that are relatively large in size. Small crystals or fines often tend to cake and cause fugitive dust emissions.
Various attempts have been made to solve the problem of small crystal size. For example, Nylander in U.S. Pat. No. 3,271,106 taught that potassium sulfate and potassium chloride crystals having relatively large crystal sizes are obtained when potassium chloride is reacted with solid potassium magnesium double sulfate in an aqueous medium in the presence of specified neutralized sulfonates. Later, Dancy in U.S. Pat. No. 4,562,058 taught that this reaction could be further improved by the use of a monosulfonated or monosulfated surfactant and a neutralized disulfonated surfactant in a weight ratio of from about 0.14 to about 0.69.
Teot, in U.S. Pat. No. 3,598,544, taught that the salts of alkyl diphenyl ether mono- or disulfonates improve the crystallization of ammonium sulfate, potassium nitrate and potassium chromate. One of the problems in the area of crystal habit modification is inability to transfer information learned from one crystal system to another. Crystallization parameters vary significantly from one crystal system to another and therefore additives that improve the crystallization of one system frequently have no impact on a different system.
Thus, there remains a need for improved methods of crystal modification in different crystal systems. This invention relates to the production of potassium chloride, more particularly to a process for enhancing the size of potassium chloride crystals.